The present invention relates generally to an improved alkaline stripper formulation, and more specifically to such a stripper formulation which may be effectively utilized on metallic surfaces having coatings of polyvinyl chloride base resin thereon. These base resin coatings are widely used as resists for various metal treating operations, such as, for example, in the chemical etching of printed circuitry, employing either flexible or rigid substrates.
In the fabrication of metallic articles which include a metallic layer or sheet disposed upon a substrate, either flexible or rigid, it is frequently desirable to employ an in-line process wherein the metal surface, coated with a photosensitive resist material such as a photosensitive polyvinyl chloride emulsion may be treated by exposure of the material to a certain desired light pattern, and thereafter developing the photosensitive material so as to permit removal of the material from the surface of the metal. Thereafter, following selected removal of the resist, the metal, while disposed on a suitable supporting substrate or base, is normally immersed in a chemical treating solution wherein a second metallic element may be plated onto the exposed metal surface. Alternatively, the exposed metal may be chemically etched and thereby either partially or completely removed. Thereafter, the remaining adherent, non-developed resist must be stripped from the surface of the metal so as to permit completion of the fabrication operation. It will be appreciated, of course, that polyvinyl chloride emulsions may be applied to the surface of a metal without necessarily being photosensitive, with such resists being applied by conventional coating techniques such as silkscreen or other masking techniques to prepare a desired pattern on the metallic surface.
The formulation of the present invention provides a non-foaming solution which permits the stripper material to be handled through conventional spray nozzles, thereby achieving highly efficient production rates with conventional equipment. It has been further found that the formulations of the present invention have exceptionally long shelf life, and also exceptionally long life in a working solution, thereby reducing the requirement of solution replenishing at frequent intervals.
In addition to the use with conventional spray nozzles, the formulations of the present invention have been found to permit long and continuous use of the material through these conventional spray nozzles. This may be accomplished without requiring unusual straining or clarification techniques, inasmuch as the material maintains the removed resist film in solution. Thus, filters and nozzles are not frequently plugged.
Therefore, it is a primary object of the present invention to provide an improved alkaline stripper for use with resist coatings, particularly resist coatings based upon polyvinyl chloride materials.
It is a further object of the present invention to provide an improved alkaline stripper for use with metallic surfaces, selected portions of which are covered with a coating of a resist material.
It is yet a further object of the present invention to provide an improved non-foaming alkaline stripper which is effective for removal of polyvinyl chloride coatings from metallic surfaces.
Other and further objects of the present invention will become apparent to those skilled in the art upon a study of the following specification and appended claims.